Display device and manufacturing method therefor

ABSTRACT

The present invention provides a display device for use in a microcapsule type electrophoretic display apparatus and a manufacturing method therefor, in which microcapsules can be aligned so as to form a monolayer, and accordingly, the microcapsules can be efficiently used. In addition, a display device is provided in which a color display can be created, positioning of the microcapsules can be easily performed, and accordingly, the contrast is improved, and a manufacturing method therefor is also provided. The display device of the present invention includes a substrate, an insulating liquid, charged color particles dispersed therein, a first electrode formed on the substrate, and a second electrode, wherein a display is created by causing the migration of the charged color particles toward the first electrode or the second electrode by a voltage applied therebetween. The microcapsules are each formed by enclosing the insulating liquid and the charged color particles in a transparent container, and the microcapsules are aligned and are enclosed in fibers composed of a light transmissive resin.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to display devices andmanufacturing methods therefor, and more particularly, relates to aelectrophoretic display device wherein a display is created by causingthe migration of charged color particles in a liquid by a voltageapplied to electrodes, and a manufacturing method therefor.

[0003] 2. Description of the Related Art

[0004] Recently, concomitant with the progress of information devices,data volume of various information has been increasing rapidly, and inaddition, output of information has been performed in various forms. Ingeneral, the output of information can be roughly classified into ascreen display using a display device, such as a cathode ray tube or aliquid crystal panel, and a hard-copy display printed on paper by aprinter or the like. In the screen display, the need for a thinnerdisplay device having a low power consumption has been growing, andabove all, a liquid crystal display device has been actively developedand commercialized as a display device which can fulfill the needdescribed above. However, for the current liquid crystal displaydevices, problems have been encountered in that letter images displayedon the screen are difficult to view depending on a viewing angle orreflection and, in addition, eyestrain caused by a flickering lightsource, low luminance, and the like has not been satisfactory solved. Inaddition, a screen display using a cathode ray tube has a similar orsuperior contrast and luminescence compared to a liquid crystal display;however, since a flicker may be generated in a screen display device,the display quality cannot be similarly compared to the hard-copydisplay described later. In addition, the device using a cathode raytube is large and heavy, and hence, the portability thereof issignificantly inferior.

[0005] It has been believed that the hard-copy displays would havedisappeared due to computerized information processing; however, asignificant amount of hard-copy output has been used in practice. Thereason for this is that when information is displayed on a screen, inaddition to the problems relating to the display quality describedabove, the resolution is generally up to 120 dpi (dots per inch) and isconsiderably inferior to a printout on paper (generally, 300 dpi ormore). Accordingly, eyestrain is larger for the screen display comparedto the hard-copy display. As a result, even when information can beviewed by the screen display, a hard-copy output is frequentlyperformed. In addition, another important reason the hard-copy displayis used even though the screen display can be used is that oncehard-copy information is output, a great deal of information can be laidout without being restricted by the size of a screen as in the case ofthe screen display, and the information thus laid out can be rearrangedand can be read one by one without performing a complicated deviceoperation. Furthermore, the hard-copy display has a superior portabilitysince no energy is required for retaining the display, and as long asthe volume of information is not significantly large, the informationcan be read at any time and at any place.

[0006] As described above, as long as a movie display or a frequentrewrite is not required, the hard-copy display has various featuresdifferent from the screen display; however, there is a shortcoming inthat a large amount of paper is consumed for a hard copy display.Accordingly, in recent years, development of rewritable recording media(recording media in which a number of cycles of recording and erasing ahigh visibility image can be performed, and no energy is required forretaining the image thereon) has been actively advancing. A rewritablethird display method which successively possesses the features of thehard-copy display described above is referred to as a paper-likedisplay.

[0007] Requirements for the paper-like display are rewritable, no energyconsumption for retaining an image or a significantly small energyconsumption therefor (memory retaining characteristic), superiorportability, superior display quality, and the like. As a display methodwhich is currently regarded as the paper-like display, for example,there may be mentioned reversible display media using a matrix systemformed of a low molecular resin or a high molecular resin (disclosed in,for example, Japanese Unexamined Patent Application Publication Nos.55-154198 and 57-82086), which performs recording/erasing by using athermal printer head. The system described above is used for displayportions of some prepaid cards; however, there are problems in that thecontrast is not so high, the number of repeatable cycles ofrecording/erasing is relatively small, such as 150 to 500 times, and thelike.

[0008] As another display method which can be used as the paper-likedisplay, an electrophoretic display device (U.S. Pat. No. 3,612,758)invented by Harold D. Lees, et al. has been known. In addition to thepatent mentioned above, Japanese Unexamined Patent ApplicationPublication No. 9-185087 also discloses an electrophoretic displaydevice. FIGS. 7A and 7B are views showing the structure and theoperation principle of these electrophoretic display devices mentionedabove. This display device includes a pair of substrates 1 and 2disposed with a predetermined spacing therebetween, and electrodes 3 and4 formed on the substrates 1 and 2, respectively. The display surface isa side indicated by the arrow B, and the electrode 4 provided at thedisplay surface side is transparent. In addition, between the twosubstrates 1 and 2, there are provided a number of charged colorparticles 5 which are positively charged and are also colored in thiscase; an insulating liquid 6 which is colored by a dye dissolved thereinso as to have a different color from that of the charged colorparticles; and partitions 13 which divide the spacing described aboveinto a number of sections in the direction along the surface of thesubstrate so as to prevent the charged color particles from beinglocalized and to define the spacing between the substrates.

[0009] In the display device described above, as shown in FIG. 7A, whena negative voltage is applied to the electrode 3 shown at the lower sidein the figure, and in addition, a positive voltage is applied to theelectrode 4 at the upper side in the figure, the charged color particles5 which are positively charged are gathered so as to cover the electrode3 at the lower side, and when this display device is viewed along the Bdirection in the figure, a display having the same color as that of theinsulating liquid 6 is created.

[0010] In contrast, as shown in FIG. 7B, when a positive voltage isapplied to the electrode 3 shown at the lower side in the figure, and inaddition, a negative voltage is applied to the electrode 4 at the upperside in the figure, the charged color particles 5 which are positivelycharged are gathered so as to cover the electrode 4 at the upper side,and when this display device is viewed along the B direction in thefigure, a display having the same color as that of the charged colorparticles 5 is created. When this operation described above is performedin each pixel unit, an optional image can be displayed by a number ofpixels.

[0011] The display device shown in FIGS. 7A and 7B creates a display bycausing the migration of the charged color particles in the directionperpendicular to the surface of the substrate in accordance with avoltage applied between the electrodes provided on the pair ofsubstrates opposing each other. In addition to this display device, adisplay device disclosed in Japanese Unexamined Patent ApplicationPublication Nos. 49-5598 and 11-202804 has been proposed in which a pairof electrodes, i.e., a first display electrode and a second displayelectrode, is disposed on the same substrate, and charged colorparticles are moved in the direction parallel to the substrate whenviewed from an observer side. This display device described abovecreates a display by causing the migration of the charged colorparticles in a transparent insulating liquid in parallel to the surfaceof the substrate and between the first display electrode and the seconddisplay electrode in accordance with a voltage applied therebetween.

[0012] In this horizontal migration type electrophoretic display device,a transparent insulating liquid is used in many cases, and when viewedfrom the observer side, the first display electrode and the seconddisplay electrode show different colors from each other, and one of thecolor of the display electrodes is the same as that of the migratingparticles. For example, in the case in which the first display electrodeis black, the second display electrode is white, and the migratingparticle is black, when the migrating particles are gathered at thefirst display electrode side, the second display electrode is exposed sothat a white color is viewed, and when the migrating particles aregathered at the second display electrode side, a black color which isthe color of the migrating particle is viewed.

[0013] In addition, recently, an electrophoretic display device usingmicrocapsules has been proposed (U.S. Pat. No. 2,551,783). In FIG. 6, across-sectional view of the electrophoretic display device using themicrocapsules is shown. Charged color particles 5 which are colored andan insulating liquid 6 which is colored so as to have a different colorfrom that of the charged color particle are enclosed in transparentcontainers 8 having a diameter of approximately 50 μm, and thesecontainers 8 are applied to a substrate 1, thereby forming a displaydevice. In order to create an image display, electrodes 3 and 4 areprovided at the top and the bottom of this microcapsules 8, and as inthe case of the conventional electrophoretic display method, a voltageis applied between the electrodes 3 and 4, whereby the color of thecharged color particles 5 or the color of the insulating liquid 6 can bedisplayed.

[0014] As for the features of the microcapsule type electrophoreticdisplay device, since the charged color particles and the insulatingliquid (that is, a dispersing liquid for migration) can be disposed bymerely applying the microcapsules to the substrate, compared to theconventional electrophoretic display device, injection steps for thecharged color particles and the insulating liquid are not required, andhence, formation of the display device can be easily performed. Inaddition, since partitions are not particularly required, for example,displacement or damage of partitions caused by warping of the substratedoes not occur, and the flexibility of the display device can beincreased.

[0015] However, in the conventional microcapsule type electrophoreticdisplay device, since the microcapsules are mixed with a binder and arethen applied to the substrate together with the binder, somemicrocapsules overlap each other or are disposed at a place at which theelectrodes are not provided, whereby there are some microcapsules whichdo not serve to create a display.

[0016] In addition, in order to create a color display, microcapsuleshaving different colors must be regularly disposed, and in the casedescribed above, a printing plate for printing a predetermined shapewith the microcapsules mixed with a binder is required, whereby there isa problem in that the manufacturing cost is increased.

[0017] As a method of disposing microcapsules in an area at whichelectrodes are provided, in addition to the printing method describedabove, as disclosed in Japanese Unexamined Patent ApplicationPublication No. 2000-35769, a method has been proposed in which by usingan ink-jet type ejection head provided with a nozzle having a diameterthrough which one microcapsule is allowed to pass, the microcapsules aresequentially ejected on desired positions on a substrate. However, inthe method described above, in addition to the difficulty of ejectingthe microcapsules one by one, there is another problem in that it isdifficult to accurately fix the microcapsules at the predeterminedpositions so as to be adjacent to each other. The reason for this isthat when the microcapsule thus ejected reaches the substrate, themicrocapsule is brought into contact with a microcapsule adjacentthereto which is previously disposed, so that the predetermined positionfor each microcapsule was displaced.

[0018] As described above, since it has been difficult to regularly andaccurately dispose the microcapsules so as to form a monolayer, themicrocapsules which are prepared cannot be efficiently used, and inaddition, the difficulty described above has been one of major obstaclesto the formation of a color display device.

[0019] In addition, since the microcapsules has a spherical shape, whena monolayer thereof is formed, gaps are formed between the microcapsulesadjacent to each other, and as a result, an effective display area isdecreased corresponding to the gaps thus formed, whereby the contrast ofthe display is decreased. As a method for avoiding the problem describedabove, it may be considered that microcapsules in a flat shape areformed by compression so as not to form the gaps between the capsules.When the microcapsules can be formed in a flat shape, the drivingvoltage can also be decreased.

[0020] However, since a microcapsule located at the edge portion of theelectrode has not a microcapsule adjacent thereto, when themicrocapsules are compressed, a part of the microcapsule located at theedge portion of the electrode is extended outside from the electrode andis adversely influenced by an adjacent electrode, and as a result, thecontrast may also be decreased in some cases. In order to form flatmicrocapsules without extending outside from the electrode, themicrocapsules must be accurately disposed at a central portion of theelectrode beforehand; however, in the case described above, a highlyaccurate alignment technique is required. In particular, as is the casein which a horizontal migration type display is performed using themicrocapsules, the phenomenon described above may become a major problemwhen microcapsules having a size approximately equivalent to that of apixel are used.

SUMMARY OF THE INVENTION

[0021] The present invention was made to solve the problems describedabove, and an object of the present invention is to provide a displaydevice for use in a microcapsule type electrophoretic display apparatusand a manufacturing method therefor, in which microcapsules can bealigned to form a monolayer structure, and accordingly, themicrocapsules can be efficiently used. In addition, another object ofthe present invention is to provide a display device and a manufacturingmethod therefor, in which a color display can be created, positioning ofthe microcapsules can be easily performed, and as a result, the contrastis improved.

[0022] That is, a display device in accordance with one aspect of thepresent invention comprises a substrate, an insulating liquid, chargedcolor particles dispersed in the insulating liquid, a first electrodeformed on the substrate, and a second substrate, in which the chargedcolor particles migrate toward the first electrode or the secondelectrode by applying a voltage therebetween so that a display iscreated. In the display device of the present invention described above,the insulating liquid and the charged color particles are enclosed inlight transmissive walls so as to form microcapsules, and themicrocapsules are aligned and are enclosed in fibers composed of thelight transmissive resin.

[0023] One line of aligned microcapsules is preferably enclosed in thelight transmissive resin fiber.

[0024] In addition, the length of the microcapsule in the directionparallel to the substrate is preferably larger than the length of themicrocapsule in the direction perpendicular to the substrate.

[0025] The fibers enclosing the microcapsules are preferably aligned onthe substrate.

[0026] In accordance with another aspect of the present invention, amethod for manufacturing an electrophoretic display device including asubstrate; an insulating liquid; charged color particles dispersed inthe insulating liquid; and a first electrode and a second electrode forapplying a voltage on the charged color particles provided on thesubstrate; in which the charged color particles migrate toward the firstelectrode or the second electrode by a voltage applied therebetween sothat a display is created, the method comprises a preparing step ofpreparing microcapsules containing the insulating liquid and the chargedcolor particles therein, a forming step of forming fibers eachcomprising a light transmissive resin and the microcapsules which arealigned and enclosed in the light transmissive resin; and a disposingstep of disposing the fibers on the substrate provided with at least oneof the first electrode and the second electrode.

[0027] The forming step described above is preferably performed byextruding the microcapsules with the light transmissive resin from anozzle so that the microcapsules are aligned and enclosed in the lighttransmissive resin.

[0028] The manufacturing method described above preferably furthercomprises a step of compressing the microcapsules into a flat shape, anda step of curing the light transmissive resin for forming the fiberswhich enclose the microcapsules in the flat shape.

[0029] In accordance with another aspect of the present invention,microcapsules for use in electrophoretic display comprise charged colorparticles, an insulating liquid in which the charged color particles aredispersed, and light transmissive walls each enclosing the charged colorparticles and the insulating liquid, wherein microcapsules in an alignedstate are enclosed in a light transmissive resin, and the lighttransmissive resin is in the form of a fiber.

[0030] Further objects, features and advantages of the present inventionwill become apparent from the following description of the preferredembodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031]FIG. 1 is a plan view showing an example of an electrophoreticdisplay device which is a display device according to the presentinvention;

[0032]FIG. 2 is a cross-sectional view taken along the line AA′ in FIG.1;

[0033]FIG. 3 is a cross-sectional view showing another example of anelectrophoretic display device taken along the line AA′ in FIG. 1;

[0034]FIG. 4 is a cross-sectional view showing another example of adisplay device according to the present invention;

[0035]FIG. 5 is a schematic view showing an apparatus for forming afiber enclosing microcapsules according to the present invention;

[0036]FIG. 6 is a schematic cross-sectional view showing a conventionaldisplay device;

[0037]FIG. 7A is a schematic cross-sectional view showing a conventionaldisplay device; and

[0038]FIG. 7B is a schematic cross-sectional view showing theconventional display device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] Hereinafter, embodiments of display devices according to thepresent invention will be described in detail with reference to FIGS. 1to 3.

[0040]FIG. 1 is a plan view showing an example of a electrophoreticdisplay device which is a display device of an embodiment according tothe present invention. FIG. 2 is a cross-sectional view taken along theline AA′ in FIG. 1. FIG. 3 is a cross-sectional view showing anotherexample of an electrophoretic display device taken along the line AA′ inFIG. 1.

[0041] In FIGS. 1 to 3, reference numeral 6 indicates an insulatingliquid; reference numeral 5 indicates charged color particles; referencenumeral 8 indicates a light transmissive microcapsule which is formed ofan insulating material and encloses the insulating liquid 6 and thecharged color particles 5; reference numeral 7 indicates a bindercomposed of a light transmissive resin; and reference numerals 1 and 2indicate a first substrate and a second substrate, respectively. Oneline of aligned microcapsules 8 is fixed by the binder 7 so as to form afiber 9, and the microcapsules are bonded to an electrode 3 or 4. InFIG. 1, the first substrate 1, the second substrate 2, the firstelectrode 3, and the second electrode 4 are omitted. In FIG. 3, thesecond substrate 2 is also omitted, and it is not always necessary inpractice.

[0042] As shown in FIGS. 1 to 3, in the display device according to thepresent invention, a dispersion composed of the insulating liquid andthe charged color particles dispersed therein is enclosed in eachcapsule, and in addition, one line of aligned capsules is enclosed in alight transmissive resin fiber. According to a method described below,the microcapsules enclosed in the resin fiber are aligned so as to be incontact with each other or to have a predetermined gap therebetween.When the resin fiber is disposed along the electrode, a regularalignment of the microcapsules can be obtained. Since the fibers arealigned one by one, compared to the case in which the microcapsules arealigned one by one, the operation is simple and can be performed in ashort period of time, and hence, superior positioning accuracy can beobtained.

[0043] In the manufacturing method described below, as shown in FIG. 5,since microcapsules compounded with a binder resin are extruded from anozzle into a fiber shape, the diameter of the fiber is determined to beapproximately equivalent to that of the nozzle. When the diameter of thenozzle is formed so as to allow one microcapsule to pass therethrough, afiber enclosing one line of aligned microcapsules can be formed. In thestep described above, the diameter of the fiber is approximatelyequivalent to that of the microcapsule. Since the fiber is formed so asto align the microcapsules, the fiber needs not have an unnecessarilywider diameter and preferably has a diameter approximately equal to thatof the microcapsule. In addition, when a cross-sectional shape of thenozzle is formed to be a rectangle, a fiber enclosing a plurality oflines of the microcapsules can be formed.

[0044] The gaps between the microcapsules enclosed in the fiber are setto a desired value by controlling the concentration of the bindercompounded with the microcapsules, the extrusion speed thereof from thenozzle, and the like. When the microcapsules enclosed in the fiber isapplied to a matrix display device described later, the gap may bedetermined in accordance with an interval between pixels. In general, itis not preferably that the gap between the microcapsules isunnecessarily large, since areas which do not serve as display areas areincreased, and the contrast is thereby decreased. In the presentinvention, by adjusting the concentration of the binder compounded withthe microcapsules, the density of the microcapsules in the nozzle, theextrusion rate, and the curing rate of the resin, the microcapsules canbe aligned with a desired gap therebetween, and particularly, themicrocapsules can also be aligned so as to be in contact with eachother.

[0045] In addition, the resin fiber has adequate rigidity or flexibilityto be aligned on the substrate, and the degree thereof differs dependingon methods for alignment on the substrate. When a cured resin fiber iscut into an appropriate length and is then disposed on a strip-shapedelectrode, the resin fiber is formed as rigid as possible, and when aresin fiber in a semi-cured state is disposed on the substrate whileextruded from the nozzle, the resin fiber is formed so as to haveflexibility. By appropriately selecting a resin material, theseproperties described above can be controlled.

[0046] When the microcapsule has a spherical shape, as described above,the gaps therebetween are formed which do not serve as a display area,resulting in a decrease in contrast. In order to realize both a decreasein gap between the microcapsules and a decrease in driving voltage, itis desired that the thickness of the display device is reduced bydeforming the microcapsule by compression or by its own weight. That is,the microcapsule preferably has a shape in which the length in thedirection parallel to the substrate is longer than the height in thedirection perpendicular thereto, and for example, a flat or an ovalshape as shown in FIG. 3, or a semispherical shape as shown in FIG. 4may be mentioned.

[0047] In the present invention, a display is created by causing themigration of the charged color particles between the first electrode 3and the second electrode 4; however, as described above, as themigration direction of the charged color particles, there are twodirections, that is, the direction (a vertical migration type)perpendicular to the substrate and the direction (a horizontal migrationtype) parallel thereto. Hereinafter, concerning these two type ofdisplay devices, embodiments according to the present invention will bedescribed.

[0048] In the vertical migration type, as shown in FIG. 2, in the casein which the first electrode 3 and the second electrode 4 are disposedto oppose each other, and observation is performed from the secondelectrode 4 side, when the charged color particles in the insulatingliquid are gathered on the first electrode 3 by applying a voltagebetween the first electrode 3 and the second electrode 4, the color ofthe insulating liquid is viewed by the observer. In contrast, when thecharged color particles are gathered on the second electrode 4, thecolor of the charged color particles is viewed by the observer. In thestructure described above, for example, when the color of the chargedcolor particles is black, and the color of the insulating liquid iswhite, a binary display by black and white can be created.

[0049] In addition, in the vertical migration type, there is a case inwhich two types of color particles having different polarities anddifferent colors from each other are dispersed in a transparentinsulating liquid so as to create a binary display. As shown in FIG. 2,in the case in which the first electrode 3 and the second electrode 4are disposed to oppose each other, and observation is performed from thesecond electrode 4 side, when each type of the charged color particlesin the insulating liquid is gathered on the electrode having thepolarity opposite to that of the charged color particles by applying avoltage between the first electrode 3 and the second electrode 4, thecolor of the charged color particles gathered on the second electrode isviewed by the observer. In the structure described above, for example,when positively charged black particles and negatively charged whiteparticles are dispersed in a transparent insulating liquid, a binarydisplay by black and white can be created. In more particular, when avoltage is applied so that the second electrode is negative and that thefirst electrode is positive, the black particles are gathered on thesecond electrode, and the white particles are gathered on the firstelectrode, whereby the black color is observed by the observer. In amanner similar to that described above, when the polarities of theelectrodes are reversed, the white particles are gathered on the secondelectrode, whereby the white color is observed by the observer.

[0050] In addition, for example, when positively charged particlecolored magenta and negatively charged white particles are dispersed ina transparent liquid, the color of the particles gathered on theelectrode located at the observer side, that is, the magenta or thewhite, is observed, whereby a binary display by magenta and white can becreated.

[0051] In the horizontal migration type, in the case in which the firstelectrode 3 and the second electrode 4 are disposed on the samesubstrate as shown in FIG. 3, and observation is performed along thedirection C shown in the figure, when charged black particles in atransparent insulating liquid are gathered on the first electrode 3 byapplying a voltage between the first electrode 3 and the secondelectrode 4, as disclosed in Japanese Unexamined Patent ApplicationPublication No. 11-202804, a black color is viewed by the observer. Incontrast, the charged black particles are gathered on the secondelectrode 4, a white color is viewed by the observer. In the structuredescribed above, as in the case described above, a binary display byblack and white can be created.

[0052] When an element performing one of the displays described above isused as one pixel, and these pixels are aligned in matrix, a displaydevice can be obtained. The fibers enclosing the microcapsules aredisposed parallel to the row direction or to the column direction in thematrix, and as shown in FIGS. 2 and 3, each fiber is in contact with thefirst electrode 3 and the second electrode 4 at each pixel portion. Whenthe diameter of the fiber is smaller than the width of the pixel, aplurality of fibers enclosing the microcapsules is disposed in the widthof the pixel. In the case of the horizontal migration type displaydevice shown in FIG. 3, since it is preferable that the diameter of themicrocapsule be approximately equal to the width of the pixel, as shownin FIG. 3, one fiber is disposed in the width of the pixel in this case.

[0053] In many color display devices, one pixel is composed of threesub-pixels having three different colors, and each sub-pixel has a stripshape continuously extending in the column direction. The microcapsuletype display device according to the present invention can be easilyapplied to a color display. That is, when fibers enclosing coloredmicrocapsules are regularly disposed as shown in FIG. 5, a color displaycan be created. For example, a color display can be created when themicrocapsules in the individual fibers are colored yellow (Y), cyan (C),and magenta (M), respectively.

[0054] As a color display, a method in which three colors are disposedin parallel and displayed so as to be visually blended, and a method inwhich three colors are laminated to each other so as to formtransmissive light having a blended color thereof may be mentioned. Thecolor display device of the present invention can be applied to bothmethods described above. In the former method, color fibers having Y, C,M, Y, C, M, and so on are regularly disposed in parallel to each otheron the substrate. In the latter method, the fibers having differentcolors are laminated so as to form a three-layered structure.

[0055] A matrix display device formed by aligning the fibers enclosingthe microcapsules described above has the following features.

[0056] First, since a monolayer alignment of the microcapsule is formed,unnecessary microcapsules overlapping with each other are not present,and hence, the microcapsules can be efficiently used.

[0057] Secondary, compared to a conventional method such as an ink-jetmethod, since the gap between the microcapsules can be reduced, a highlydense alignment can be realized, and hence, the contrast can beincreased.

[0058] Thirdly, since one line of the aligned microcapsules is enclosedin the fiber, when the microcapsules are compressed into a flat shape,uniform deformation thereof can be obtained, and they do not extendoutside from the width of the electrode. Accordingly, no adverseinfluence from adjacent pixels is present, and hence, a high contrastcan be obtained.

[0059] Next, a method for manufacturing the display device of thepresent invention will be described.

[0060] An example of a method for manufacturing a display device of anembodiment according to the present invention will be described withreference to FIGS. 2 and 5. First, in microcapsules composed of aninsulating material having light transmittance, an insulating liquid andcharged color particles dispersed therein are enclosed. Themicrocapsules can be formed by a known technique. An interfacialpolymerization method disclosed in, for example, Japanese UnexaminedPatent Application Publication Nos. 10-149118 or 11-119264 is preferablyused.

[0061] In addition, in this embodiment, an example will be described inwhich gelatin is used as a material for forming a capsule wall; however,the material for forming the capsule wall is not limited thereto. Forexample, various compounds, various polymers, and various copolymers,such as polyvinyl acetate, ethyl cellulose, nitro cellulose,polystyrene, polyethylene, polypropylene, epoxy resins, acrylic resins,methacrylic resins, nylons, polyesters, polycarbonates, polyvinylchloride, polyvinyl alcohol, and sodium alginate, can be used.

[0062] As the insulating liquid enclosed in the microcapsule, there maybe mentioned an aromatic hydrocarbon, such as toluene or xylene; analiphatic hydrocarbon, such as a normal paraffin or an isoparaffin; or ahalogenated hydrocarbon. Among these mentioned above, an isoparaffin ora silicone oil is preferably used. In addition, a liquid having a lowviscosity is preferable. As for the insulating liquid, in order to havea specific gravity equivalent to that of the charged color particle, aplurality of insulating liquids having different specific gravities fromeach other may be mixed together in some cases. When the insulatingliquid is colored, an oil-soluble dye or pigment is used.

[0063] As the charged color particle, an organic or an inorganicmaterial may be used which migrates in an insulating liquid by anelectric field applied thereto and is in the form of a fine particle.The color of the charged color particle may be a color of the materialitself or a color formed by adding a coloring agent. In addition, thecharged color particle may be formed of a single material or may beformed of a plurality of materials. In particular, as a white particle,titanium oxide or aluminum oxide is preferably used, and as a blackparticle or a particle having another color, a resin, such aspolyethylene, polystyrene, or an acrylic resin, mixed with a coloringagent is preferably used. As the coloring agent, in addition to carbon,various known dyes or pigments, such as phthalocyanine blue, lake red,and hanza yellow, can be used. In addition, a charge-control agent maybe used when necessary. As the size of the charged color particle, aparticle having a diameter in the range of from 0.1 to 50 μm ispreferably used, and more preferably, in the range of from 0.1 to 10 μm.

[0064] The microcapsules thus formed are compounded with a binder, suchas a water-soluble silicone resin or an acrylic resin, and as shown inFIG. 5, are extruded by an extruder 11 provided with a nozzle 10 havingan inside diameter (preferably, in the range of from 30 to 500 μm)approximately equal to the diameter of the capsule, so that a fibershape is formed. In the step described above, the gaps between thecapsules can be controlled by adjusting the viscosity of the binder andthe concentration of the microcapsules in the binder material. An esterresin or a urethane resin may also be used as the binder material. Theinside diameter of the nozzle is more preferably in the range of from 50to 300 μm.

[0065] The shape of the fiber is not specifically limited, and forexample, a cross-section having a quadrangular, a triangular, acircular, or an oval shape may be used, and in addition, a combinationthereof may also be used.

[0066] Next, the fibers enclosing the microcapsules thus formed aredisposed on the substrate by steps described below.

[0067] First, the vertical migration type display device will bedescribed with reference to FIG. 2.

[0068] On the first substrate 1, the first electrode 3 is formed. As amaterial for the substrate, a glass or a plastic film is used. As asubstrate at an observer side, a light transmissive material, such asglass or quartz, may be used, and preferably, a resin film formed ofpolyethylene phthalate (PET), polyether sulfone (PES), or the like isused.

[0069] A material for forming the first electrode 3 is not specificallylimited; however, in general, a metal electrode such as aluminum (Al) isused. On the first substrate 1, the fibers enclosing the microcapsulesdescribed above are disposed along the first electrode 3 so as to form amonolayer. In the step described above, fibers immediately afterextruded from the nozzle, which are in a semi-cured state, may bedisposed on the electrode while the nozzle is moved with respect to thesubstrate, or fibers which are cured and cut beforehand and have alinearity may be disposed on the electrode. When a binder has anadhesive property as an adhesive, an adhesive is not specificallyrequired; however, an adhesive such as a light transmissive resin may besecondarily used.

[0070] As the second electrode 4, a transparent electrode composed of,for example, an ITO film or an organic conductive film is used.

[0071] Next, the horizontal migration type display device will bedescribed with reference to FIG. 3. On the first substrate 1, the firstelectrode 3 is formed. A material for forming the substrate is the sameas that used in the vertical migration type. As the first electrode 3, alight-reflective metal electrode such as Al is generally used. On thefirst electrode 3, a light-scattering insulating layer is provided. Forexample, a layer composed of a transparent insulating resin andparticles for scattering light, such as aluminum oxide or titaniumoxide, mixed therewith is formed.

[0072] Alternatively, without using fine particles, a method forscattering light by using irregularity of the surface of the metalelectrode may be employed.

[0073] Next, the second electrode 4 is formed on the insulating layer.As a material for forming the second electrode 4, a conductive materialis used having a black color, such as titanium carbide, chromiumprocessed by blackening treatment, or aluminum or titanium having ablack layer thereon, when viewed from the observer side for the displaydevice.

[0074] Next, on the second electrode 4, the fibers enclosing themicrocapsules are disposed so as to form a layer. After the fibers aredisposed on the second electrode 4, the microcapsules are deformed intoa flat shape by applying a pressure thereto, and subsequently, thebinder is preferably cured while the microcapsules are in a flat shape.However, when the binder has a low viscosity, and each capsules has aflexible wall, without applying a pressure to the capsules, the capsulesmay be deformed by its own weight.

[0075] Alternatively, fibers which are cured so as to have a flat shapebeforehand may be disposed on the substrate one by one.

[0076] The display device can be obtained by connecting a voltage applycircuit to the first and the second electrodes 3 and 4. At the upperside of the display device (at the observer side), the substrate may beprovided or may not be provided.

[0077] The method for manufacturing the microcapsule display deviceaccording to the present invention has the features described below.

[0078] First, since the rigid fibers are disposed, or the fibers aredisposed by moving the nozzle, the capsules can be easily disposedlinearly with superior accuracy.

[0079] Secondary, since the electrodes or signal lines are patterned onat least one substrate, the fibers may be merely disposed on thesubstrate in accordance with the electrode positions, and hence, thepositioning accuracy of the fibers with respect to the electrodepositions is superior.

[0080] Thirdly, when the microcapsules are deformed into a flat shape bycompression or by its own weight, since the microcapsules are fixed inthe resin, they are not displaced, and as a result, the microcapsules donot extend outside from the electrode.

[0081] Hereinafter, the present invention will be described in detailwith reference to examples.

EXAMPLE 1

[0082] A display device shown in FIG. 2 was formed.

[0083] An isoparaffin colored by an oleophilic blue dye was used as theinsulating liquid, and yellow particles used as charged color particles,which were composed of a yellow-colored polystyrene having a particlediameter of 1 to 2 μm, were mixed with and dispersed in the insulatingliquid described above so as to form a dispersion containing 3 wt % ofthe yellow particles. Subsequently, microcapsules each having a flexiblewall composed of gelatin and enclosing this dispersion were formed by atypical coacervation method.

[0084] The microcapsules thus formed had a wall thickness of 2 to 4 μm,and a diameter of 100 to 120 μm. These microcapsules were mixed with anaqueous solution containing 30 wt % of polyvinyl alcohol, were receivedin an extruder provided with a nozzle having an inside diameter of 100μm, and were extruded therefrom so as to form fibers enclosing themicrocapsules. Subsequently, the fibers thus formed were disposed on thesubstrate. The substrate was formed of a first substrate 3 composed of aPET film 200 μm thick and the first electrode 3 composed of aluminumpatterned on the first substrate 3. The fibers were disposed on thissubstrate, were dried, and were bonded thereto by applying heat.

[0085] After a binder layer formed of an aqueous solution containingpolyvinyl alcohol was dried, a substrate composed of a second substrate2 formed of a PET film and an ITO film formed thereon as a secondelectrode 4 was bonded to the surface of the fiber layer by a lighttransmissive adhesive so that the fibers and the substrate were broughtinto close contact with each other, and voltage apply means was providedtherefor, whereby the display device was formed.

[0086] Display was performed by using the display device thus formed.The applying voltage was set to be ±50 V. The charged color particlesused in this example were positively charged in the isoparaffin andmigrated to an electrode to which a negative voltage is applied. Theresponse rate was 30 millisecond or less, and irregularity on thedisplay was not observed.

EXAMPLE 2

[0087] A display device shown in FIG. 3 was formed.

[0088] Isoparaffin was used as the insulating liquid, and blackparticles as charged color particles, which had a particle diameter of 1to 2 μm and were composed of polystyrene and carbon, were mixed with anddispersed in the insulating liquid described above so as to form adispersion containing 3 wt % of the black particles. Subsequently,microcapsules formed in a manner equivalent to that described in Example1 were mixed with an aqueous solution containing polyvinyl alcoholhaving 30 wt % of a stilbazolium group, were received in an extruderprovided with a nozzle having an inside diameter of 100 μm, and werethen extruded therefrom so as to form fibers enclosing themicrocapsules.

[0089] An aluminum layer used as a first electrode 3 was formed on afirst substrate 1 composed of a PES film. A light-scattering insulatinglayer was provided on the first electrode 3. Next, as second electrodes4, a black titanium carbide film was formed on the insulating layer andwas then patterned to form strip shapes by a photolithographic methodand a dry etching method. The line width was set to 25 μm, and thedistance between lines was set to 100 μm.

[0090] The fibers enclosing the capsules were placed on the secondelectrodes 4, were dried, and were then bonded thereto. After the fiberswere dried, the fiber and the substrate were brought into close contactwith each other, and voltage apply means was provided therefor, wherebythe display device was formed.

[0091] A PET substrate was placed on the upper surface of the fibersenclosing the microcapsules, the capsules in the fibers were deformedinto a flat shape by applying a pressure thereto using a roller, andsubsequently, the fibers were cured by irradiation of ultraviolet rays.On the upper surfaces of the fibers enclosing the capsules, a lighttransmissive film was formed as a protective film. Next, voltage applymeans was provided therefor, whereby the display device was formed.

[0092] Display was performed by using the display device thus formed.The charged color particles were positively charged in the isoparaffinand migrated toward an electrode to which a negative voltage is applied.In the step described above, irregularity on the display was notobserved.

EXAMPLE 3

[0093] Microcapsules were formed in a manner similar to that of Example2.

[0094] The microcapsules described above each had a wall thickness of 5μm and a diameter of approximately 200 μm. These microcapsules weremixed with an aqueous solution containing 20 wt % of polyvinyl alcohol,were received in an extruder provided with a nozzle having an insidediameter of 200 μm, and were extruded therefrom, thereby forming fibersenclosing the microcapsules. The fibers thus formed were disposed inparallel on a substrate and were bonded thereto, and subsequently, thefibers were cured. The substrate used in this example was equivalent tothat in Example 2. Before the fibers were cured, the capsules weredeformed into a semispherical shape by its own weight. On the uppersurfaces of the fibers enclosing the capsules, a light transmissive filmwas formed as a protective film. Next, voltage apply means was providedtherefor, whereby a display device was formed.

[0095] Display was performed by using the display device thus formed.The charged color particles were positively charged in the isoparaffinand migrated toward an electrode to which a negative voltage is applied.In the step described above, irregularity on the display was notobserved.

EXAMPLE 4

[0096] A silicone oil was used as the insulating liquid, and three typesof color particles used as charged color particles, each having aparticle diameter of 1 to 2 μm and composed of polystyrene and one of ayellow, a cyan, and a magenta coloring dye, were respectively mixed withand dispersed in the insulating liquid described above so as to formdispersions each containing 3 wt % of the color particles describedabove.

[0097] Fibers enclosing microcapsules were formed in a manner similar tothat in Example 1, were disposed on the same second electrode 4 as thatdescribed above and bonded thereto so that the individual colors aredisposed in order, and subsequently, the fibers were cured. On the uppersurfaces of the fibers, a light transmissive film was formed as aprotective film. Next, voltage apply means was provided therefor,thereby forming a display device.

[0098] Display was performed by using the display device thus formed.The charged color particles were positively charged in the silicone oiland migrated toward an electrode to which a negative voltage is applied.In the step described above, irregularity on the display was notobserved, and a color display could be created.

EXAMPLE 5

[0099] A silicone oil was used as the insulating liquid, and three typesof color particles used as charged color particles, each having aparticle diameter of 1 to 2 μm and composed of polystyrene and one of ayellow, a cyan, and a magenta coloring dye, were respectively mixed withand dispersed in the insulating liquid described above so as to formdispersions each containing 3 wt % of the color particles describedabove.

[0100] Fibers enclosing microcapsules were formed in a manner equivalentto that in Example 1, were disposed on the same second electrode 4 asthat described above, and were then bonded thereto. A PET substrate wasplaced on the upper surfaces of the fibers, and a pressure was appliedto the PET substrate by using a roller so as to deform the capsulesenclosed in the fiber into a flat shape. The fibers were then cured, andsubsequently, the PET substrate was removed. On the upper surfaces ofthe fibers, a light transmissive film was formed as a protective film,and voltage apply means was then provided therefor, whereby a displaydevice was formed.

[0101] Display was performed by using the display device thus formed.The charged color particles were positively charged in the silicone oiland migrated toward an electrode to which a negative voltage is applied.In the step described above, irregularity on the display was notobserved, and a color display could be created.

EXAMPLE 6

[0102] An isoparaffin was used as an insulating liquid, and three typesof color particles used as charged color particles, each having aparticle diameter of 1 to 2 μm and composed of polystyrene and one of ayellow, a cyan, and a magenta coloring dye, were respectively mixed withand dispersed in the insulating liquid described above so as to formdispersions each containing 3 wt % of the color particles describedabove. In a manner equivalent to that in Example 3, fibers enclosingmicrocapsules were formed, were disposed on a first substrate 1, andwere then bonded thereto. Subsequently, the fibers were cured. Beforethe fibers were cured, the microcapsules were deformed into asemispherical shape by its own weight. On the upper surfaces of thefibers, a light transmissive film was formed as a protective film.Voltage apply means was then provided therefor, whereby a display devicewas formed.

[0103] Display was performed by using the display device thus formed.The charged color particles were positively charged in the isoparaffinand migrated toward an electrode to which a negative voltage is applied.In the step described above, irregularity on the display was notobserved, and a color display could be created.

[0104] As has thus been described, in the microcapsule typeelectrophoretic display device according to the present invention, themicrocapsules mixed with the binder can be aligned to form a monolayeron the substrate, and hence, the microcapsules prepared can beefficiently used. In addition, a color display can be created by thedisplay device using these microcapsules.

[0105] In addition, the shape of the microcapsules can be changed from asphere to a shape in which the length in the direction parallel to thesurface of the substrate is larger than the length in the directionperpendicular thereto. Accordingly, since the gaps, which do not serveas a display area, formed between the microcapsules can be reduced, thecontrast can be improved, and in addition, a driving voltage can also bereduced by decreasing the thickness of the display device portion.

[0106] While the present invention has been described with reference towhat are presently considered to be the preferred embodiments, it is tobe understood that the invention is not limited to the disclosedembodiments. On the contrary, the invention is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims. The scope of the following claims is to beaccorded the broadest interpretation so as to encompass all suchmodifications and equivalent structures and functions.

What is claimed is:
 1. A display device comprising: a substrate; aninsulating liquid; charged color particles dispersed in the insulatingliquid; a first electrode formed on the substrate; and a secondelectrode; wherein the charged color particles migrate between the firstelectrode and the second electrode by applying a voltage therebetween sothat a display is created, the insulating liquid and the charged colorparticles are enclosed in transparent containers so as to formmicrocapsules, and the microcapsules are aligned and are enclosed inresin fibers composed of the light transmissive resin.
 2. A displaydevice according to claim 1, wherein one line of aligned microcapsulesis enclosed in each resin fiber.
 3. A display device according to claim2, wherein the diameter of the resin fiber is approximately equal to thediameter of the microcapsule.
 4. A display device according to claim 1,wherein the length of the microcapsule in the direction parallel to thesubstrate is larger than the length of the microcapsule in the directionperpendicular to the substrate.
 5. A display device according to claim4, wherein the microcapsule has a flat spheroidal shape.
 6. A displaydevice according to claim 4, wherein the microcapsule has asemispherical shape.
 7. A display device according to claim 1, whereinthe resin fibers enclosing the microcapsules therein are aligned on thesubstrate.
 8. A display device according to claim 7, wherein themicrocapsules enclosed in each resin fiber show a color of one ofyellow, cyan, and magenta.
 9. A method for manufacturing anelectrophoretic display device including a substrate; an insulatingliquid; charged color particles dispersed in the insulating liquid; anda first electrode and a second electrode provided on the substrate forapplying a voltage to the insulating liquid; in which the charged colorparticles migrate between the first electrode and the second electrodeby applying a voltage therebetween so that a display is created, themethod comprising: a preparing step of preparing microcapsulescomprising the insulating liquid and the charged color particlestherein; a forming step of forming fibers each comprising a lighttransmissive resin and the microcapsules which are aligned and enclosedin the light transmissive resin; and a disposing step of disposing thefibers on the substrate provided with at least one of the firstelectrode and the second electrode.
 10. A method for manufacturing anelectrophoretic display device, according to claim 9, wherein theforming step is a step of forming the fibers by extruding themicrocapsules with the light transmissive resin from a nozzle so thatthe microcapsules are aligned and enclosed in the light transmissiveresin.
 11. A method for manufacturing an electrophoretic display device,according to claim 10, wherein the disposing step is a step of disposingfibers, which are extruded from the nozzle and in a semi-cured state, onthe substrate by moving the nozzle.
 12. A method for manufacturing anelectrophoretic display device, according to claim 10, wherein thedisposing step is a step of disposing fibers, which are cured and have apredetermined length, on the substrate.
 13. A method for manufacturingan electrophoretic display device, according to claim 9, furthercomprising a step of compressing the microcapsules into a flat shape,and a step of curing the light transmissive resin for forming the fiberswhich enclose the microcapsules in the flat shape.
 14. A method formanufacturing an electrophoretic display device, according to claim 9,further comprising a step of curing the light transmissive resin forforming the fibers which enclose microcapsules in a deformed state byits own weight.
 15. A method for manufacturing an electrophoreticdisplay device, according to claim 9, wherein the disposing step is astep of aligning fibers having a plurality of colors on the substrate.16. Microcapsules for use in an electrophoretic display comprising:charged color particles; an insulating liquid in which the charged colorparticles are dispersed; and transparent containers each enclosing thecharged color particles and the insulating liquid; wherein themicrocapsules in an aligned state are enclosed in a light transmissiveresin, and the light transmissive resin is in the form of a fiber.